PAR - OpenID Connect Authentication

Pushed Authorization Request (PAR) allows clients to push the payload of an OIDC authorization request to CAS via a direct request. The result of this push provides clients with a request URI that is used as reference to the data in a subsequent call to the authorization endpoint via the user-agent.

PAR fosters security by providing clients a simple means for a confidential and integrity protected authorization request. Clients requiring an even higher security level, especially cryptographically confirmed non-repudiation, are able to use JWT-based request objects in conjunction with a pushed authorization request.

PAR allows CAS to authenticate the client before any user interaction happens. The increased confidence in the identity of the client during the authorization process allows the authorization server to refuse illegitimate requests much earlier in the process, which can prevent attempts to spoof clients or otherwise tamper with or misuse an authorization request.

A typical exchange would allow the client to push the authorization request via POST to the oidcPushAuthorize endpoint. The result of this request typically would produce a request_uri as such:

{
  "expires_in": 30,
  "request_uri": "OPAR-1-..."
}

The request_uri parameter could then be submitted back to CAS’ authorization endpoint to restore and resume the request.

Configuration

The following settings and properties are available from the CAS configuration catalog:

cas.authn.oidc.par.max-time-to-live-in-secondsHard timeout to kill the PAR token and expire it.

PT30S

Duration

Hard timeout to kill the PAR token and expire it.

Type: String
Default: PT30S
Defined by: OidcPushedAuthorizationProperties

cas.authn.oidc.par.number-of-usesControls number of times a request can be used within CAS server.

1

Controls number of times a request can be used within CAS server.

Type: Long
Default: 1
Defined by: OidcPushedAuthorizationProperties

cas.authn.oidc.par.storage-nameThe storage object name used and created by CAS to hold PARs in the backing ticket registry implementation.

oidcPushedAuthzRequestsCache

The storage object name used and created by CAS to hold PARs in the backing ticket registry implementation.

Type: String
Default: oidcPushedAuthzRequestsCache
Defined by: OidcPushedAuthorizationProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Notes on configuration

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, especially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.